1. Field of the Invention
The present invention relates to an imaging apparatus using an electron multiplying solid-state image pickup device and a gain adjusting method for the same.
2. Related Background Art
Recently, an electron multiplying CCD (EM-CCD) has been developed and used as a solid-state image pickup device having an electron multiplying function. In the EM-CCD, a multiplier register is provided for a horizontal shift register which outputs charge signals from respective pixels of an imaging section, and in this multiplier register, by transferring charges by a voltage higher than normal, the charge signals are multiplied (for example, refer to Patent document 1: Japanese Patent Application Laid-Open No. 2006-203222, Patent document 2: Japanese Patent Publication No. 3483261, and Patent document 3: Japanese Patent Publication No. 3862850).
Herein, at the time of fluorescent observation of a sample such as a cell with a fluorescence microscope, fluorescence from the sample may be weak, so that it may be difficult to acquire an image at a sufficient sensitivity by using a normal image pickup device. On the other hand, the EM-CCD camera using the above-described electron multiplying CCD is useful for acquiring an image including such weak light at a high sensitivity as well as an ICCD camera and an EB-CCD camera, etc., which also have the electron multiplying function. The EM-CCD camera can be preferably used in various fields that require image acquisition at a high sensitivity as well as measurement of weak light in the above-described fluorescence observation.